Numerous valve actuators, and particularly valve actuators for heating/cooling valves, incorporate an electric motor as the primary power source to operably drive the valve between open and closed conditions. A gear train amplifies and transfers the torque from the motor to the valve. More particularly, the valve actuator rotates a valve member or manipulates a fluid control device, typically a ball, between the open and closed conditions.
Some valve actuators incorporate a return spring coupled to the gear train to drive the gear train in the opposite direction and return the valve member to a predetermined position when power is removed from the motor. The return spring is stretched as the gear train is driven by the electric motor and stores potential energy until the electric motor is de-energized. When the motor is de-energized the return spring contracts and back drives the gear train returning the valve member to the desired predetermined position, e.g. an open position or a closed position.
For example, a normally closed configuration will be configured such that if power is lost, the return spring will back drive the gear train to a predetermined position in which the actuator closes the valve, through the use of the mechanical energy stored in the spring. Conversely, a normally open configuration will be configured such that if power is lost, the return spring will back drive the gear train to a predetermined position in which the actuator opens the valve, through the use of the mechanical energy stored in the spring.
Depending on the configuration of the valve, a valve actuator that operates in a clockwise direction or a valve actuator that operates in a counter-clockwise direction may be required.
In some valve actuators, it is desired to be able to manually set the position of the valve member via the valve actuator using a manual positioning lever of the valve actuator coupled to the gear train. As the user manually sets the position of the valve member, the return spring is stretched to store potential energy for ultimately back driving the system to the predetermined position. However, without any resistance acting against the return spring by the electric motor, the valve actuator cannot remain in the manually set position.
This invention pertains to improvements in valve actuators that permit manually setting the position or orientation of the valve member coupled to the valve actuator.